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Heater Output

Dayton Murdock

Well Known Member
Hi Everyone
My heater output dismal at best. The air inlet is on the back baffle then it goes thru the heat muff thru the firewall via a firewall shuttle to the center stick area that I made into a plentum and then out 2 eyeball vents. I can feel warm air just not very much of it. What have other builders done? :confused:
 
Hi Dayton,
I'm putting together a similar system in my -4, only there's one eyeball vent in the front and one in the back. (yes, I'm one of the crazy people who bored a hole in the spar) I've noticed in other aircraft I don't feal much air, but you feal warm. Is this your case too, or is it not enough to keep you warm? I'm curious to see what others have done also, as I haven't attached anything firewall forward yet. Perhaps a small blower along the line?
 
try robins heat muff. goes over both exhaust pipes. where are you getting the air flow from. mine is on the back just behind #3 cylinder. plenty of and and good heat.

dan carley
rv-4
N2275S
 
Dayton
I just flew my 8 today with a new muff installed in series with the old one.
I had much more heat today. The old setup was as follows:
2" flange on the rear baffle(angled part). Foil tape over the inlet with a 1" hole (after experimenting). Standard Van's triangular heat box on firewall.
Heat muff on newer Vetterman 2" tail pipes.
Results were, my right foot stayed warm!
New setup:
I had a muff on the front crossover tube to feed the carb heat with the fresh air supplied from the left front baffle. So I added another muff to the other front crossover tube and put a "Y" on the inlet at the front baffle. It feeds both front muffs. The new muff's outlet goes to the inlet of the old muff.
I taped over the old inlet on the back baffle.
Results were: oat 26 deg. F, Right leg roasting, warm air could be felt by rear seat ballast(he told me so).
I believe 2 muffs in series is the way to go and it seems like there is more airflow from the front baffle.
 
Brrrrrr.....

Dayton,

Living in SD for 4 winters and flying in AK I learned a couple of heater tricks from the locals.
First, seal every cockpit air leak you have with tape and duct seal from the Home Depot aviation dept. The worst leak areas are the stick wells, flap pushrod tube holes and rear canopy seal.
Second, take your muff off and install (wrap) a bedspring around the exhaust pipe underneath the heat muff. This acts as a heatsink and nearly doubles the heat coming out of the muff. To increase the heat volume, decrease the input air into the muff. I have a 1" scat on my muff input, 2" exit. It allows for expansion, the old science class experiment in action.
All these combined with wool socks and a good set of longjohns really helped. Be advised, in Alaska we ceased all piston powered airplane flying at -50, hopefully you're not that motivated to fly when it's that cold. Another key number is +32F/0C. Lycoming recommends pre-heating below this temp, I use a hair-dryer and a JC Whitney auto dipstick heater, multi-vis Aeroshell rules!

Have Fun!

Smokey
 
Heater

Hi Smokey

Over this pass weekend I accomplish some of the task you describe. I sealed my canopy at the aft edge and along the hinge. I used some hockey tape on top of my fuselage as an anti-chafe surface and 1/16? X 3/8? foam tape from the hobby store along the canopy edge to seal the gap. My push rod tubes and stick wells are sealed up. I will try to change out the input tube to 1? dia and install the door spring on my exhaust pipe.

Rob where do you have your heated air eyeball vent in your cockpit? Do you have it doing double duty as a fresh air vent also?
 
The heat is on....

Dayton,
I have one of the stainless fireproof heater boxes on my firewall going into the cockpit under the right rudder pedal. I took an idea from my Dad's Cessna 140 and put a diverter in front of it that moves the air to the side. The rear passenger gets heat except on the coldest of southern days. I have separate NACA vents and 2 Larry Vetterman flip-out vents for fresh air...

RR
 
Engine Heat

Being a LONG time, high time GA pilot of certified aircraft in MI, I fly to the UP a lot in the winter, I came up with a few great ways to heat. The best, and I wrote and article in CPA that was published (you can look it up), is to go to Home Depot/Lowes and buy good dryer vent material, a metal connection (or use alum tape) and a ceramic heater. Set it up to blow in whatever works for your aircraft and turn it on the day before. If you direct the heat from the lower cowl, it heats up the entire engine compartment, oil included (and battery if in that area). Lay a blanket over the cowl. Previously I had all the other commercially available heaters (Tanis, Reiff)... NONE work as good as this.
 
Robins no reply....

Can't seem to get a hold of Rick at Robins...any suggestions?
I have a RV6A with O320, one heat muff right pipe. Planning ahead for winter flying, I heard adding a second to the other pipe is worth doing. Also, I have no heat from the heat muff going into the carb (appears like only warmer air in engine compartment). Input for COLD winter flying would be appreciated??
 
When I bought my RV-8 it had a Vetterman exhaust system that did not provide much heat. Northern Illinois gets cold so I changed to a 4 into 1 from AWI which had studs welded onto the exhaust in the area where the heat cuff goes. Now I get LOTS of heat. More than my tootsies can stand. I need a diverter to get the hot air away from my toes but I now live in North Texas which does not see quite as much cold weather. I only need to crack open the firewall flapper half way and get all the heat I need.

The idea is to get more square inches of hot material in the way of the air flow. The bedspring idea sounds great. I have also read on this site people having good success by packing some stainless steel steel wool in the heat cuff.

I am sure Larry V. has a good reason for not putting studs on. He's a smart and practical guy. I've had the AWI system on for 6 years and have had no problems. I check the studs every year or so and I don't see any cracking so it seems like a good way to get a lot of heat.
 
From Larry Vetterman

I asked Larry to respond to this thread as he has far more direct experience with testing heating systems than I do. Clint

This is a response to the post on cabin heat on VAF. First of all there are some 40 different models of exhaust systems for all of the engine-airframe combinations so advising on one system may not be appropriate for others. On the RV-4, the one I have the most time in, I spent a lot of time on heat muffs and getting it into the cabin. The best muff I found is the Robbins Wings muff that goes around 2 pipes, number 1-3. The temperature of the incoming air depends on a number of things like how fast the air is going thru the muff. Too fast and it doesn't have much time to transfer heat and warm it up. Then what are the egt's. The hotter the egt is, the warmer the air will be. Then the OAT is a big one. I flew many times at 0 and was comfortable with a jacket. Lastly, how many air leaks are there? That little draft in the summer time becomes an unbearable arctic blast in the winter. The -4 is a hard one to seal up especially around the canopy. The old subject of tail pumping was really going on in my -4, so I installed a reverse NACA vent in the belly, and it made all the difference. I remember after I had it installed, my wife went on a flight and she asked me what I had changed as her hair was not blowing forward back there. So it worked.
Getting heat to the back is a problem, so after many attempts I settled on a section of scat tubing mounted temporarily. She could move it around at will and it worked.
I also tested the welded on studs on 2 separate systems and did not get any temperature change with or without them, so I never endorsed them. Your experience with them may be different than mine.
On most crossover systems on the 0-320 and 0-360 systems one cabin heat muff usually is enough but the system was designed to install one on each side. Then when we designed the muffler system, heat was never a problem as that setup with the muffler can and shroud puts out way more heat than needed.
By the way, Robbins Wings is still doing muffs, he's just out of town right now. Hope some of the above info helps. Larry Vetterman
 
+1

Seems like it's all been covered at this point, but I'll add that I've comfortably flown my -4 in sub-zero temps with the Robbins muff (firewall port only), good canopy seals, and cheap seat heating pads from Amazon.

Of the 3, the $15 seat heaters made the biggest difference for both front and rear occupants in normal winter operations. A blanket goes a long way in compensating for previously-undetected canopy leaks.

At single-digit (f) temps, I start to worry about the stress I'm putting on the canopy and fiberglass parts, and whether my car will start when I get back to the hangar. Of course, oil temps, engine preheating, and off-field survival gear are worthy considerations, too.

As far as I'm concerned, a good day of flying is always better than a good day of ice fishing.

M
 
Dead horse starting to quiver...

I usually hop into these discussions of heaters at about this point, noting that a counter-flow heat exchanger is more effective than a concurrent flow one. This is a very basic mechanical engineering principle in heat exchangers such as our heat muffs.

What it means is the cold air should be put into the muff at the aft end, while the warm air exits the forward end of the muff. I.e., exhaust goes one way, heated air the opposite; hence the description counter-flow. The reason this is more effective is that the average local temperature differential from inside the pipe to outside is maximized. Temperature differential drives heat transfer.

About 98% of all planes I've observed have this wrong. I do not know what the effectiveness change is, but it is free to do this, so why not?
 
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